1. Field of the Invention
The present invention relates generally to in-wheel motors and particularly to in-wheel motors capable of efficiently cooling an electric motor and a reduction gear.
2. Description of the Background Art
Conventional in-wheel motors include an electric motor, a reduction gear and a case. The electric motor includes a stator iron core, a stator coil and a rotor. The reduction gear is formed of a planetary gear unit.
The case is formed of a case associated with the vehicle and arranged closer to the center of the vehicle, and a case associated with a wheel and arranged closer to a wheel disc. The case associated with the vehicle is in the form of a dish and that associated with the wheel is in the form of a cup and fixed to the case associated with the vehicle.
The electric motor and the reduction gear are accommodated in the disc associated with the wheel. The electric motor's stator iron core is fixed to the case associated with the wheel. The stator coil is wound around the stator iron core. The rotor is arranged inner than the stator iron core and the stator coil. The reduction gear is arranged adjacent to the electric motor and fixed to the case associated with the wheel (Japanese Patent Laying-Open No. 10-42518).
Thus conventional in-wheel motors have an electric motor and a reduction gear fixed to the case associated with the wheel.
In other words, the conventional in-wheel motors do not have the electric motor or the reduction gear fixed to the vehicle-associated case, which serves as a path of cooling air, and thus have a disadvantageously limited capability to cool the electric motor and the reduction gear.